This technique is used for the manufacture of metal armatures, for instance, stators and rotors for electric motors, transformers, remote control switches, etc.
The proportioning of the sheet pack to be separated from the sheet stack is made difficult by the fact that, for a predefined height of the sheet pack, no one knows the number of sheets comprising it and thus no one can determine the division line between the last upper sheet of the pack and the next lower sheet of the stack which constitutes the first lower sheet of the subsequent pack. This is due to the tolerances in the thickness of the plate from which individual sheets are trimmed. Owing to the tolerances of these plates, when the pack is separated from the overlying stack of sheets, the last upper sheet still belonging to the separated pack can still be held temporarily at the lower end of the overlying stack of sheets by means intended to block it in the magazine. For instance, the last upper sheet may be engaged by said means only for a small portion of its thickness. Therefore, in these conditions, the separated sheet pack is missing a sheet and is thus undersized. Furthermore, the last sheet belonging to the separated pack and precariously held against the overlying stack can detach itself from the stack at any time and, falling in an uncontrolled manner, can damage and jam the device.
The last sheet of the separated pack can also be precariously held against the stack itself, because of a moderate sticking or adhesion effect due, for instance, to the presence of trimming lubricants, oxides, material annealing, or other similar causes.